NTSB Factual Report

On July 10, 2012, about 1545 central daylight time, a Maule M-4, N12026, ground looped during a landing on runway 31 (3,400 feet by 75 feet, dry asphalt) at the Springfield Municipal Airport (D42), near Springfield, Minnesota. The private pilot and the flight instructor passenger were not injured. The airplane’s left wing was substantially damaged. The airplane was registered to a private individual and operated by the pilot, under the provisions of 14 Code of Federal Regulations (CFR) Part 91 as a personal flight. Day visual flight rules conditions prevailed for the flight, which did not operate on a VFR flight plan. The local flight originated from the New Ulm Municipal Airport (ULM), near New Ulm, Minnesota, about 1410.

According to the pilot’s accident report, a new engine had been installed in the accident airplane and a local flight was conducted in the ULM area that was about an hour in duration. A mechanic examined the engine and the airplane was subsequently flown to Sleepy Eye Municipal Airport (Y58), near Sleepy Eye, Minnesota, where 11 landings to a full stop were conducted on the grass strip there. This flight returned to ULM and its duration was 1.5 hours. The aircraft was refueled. The pilot and flight instructor flew to Y58 for 10 more landings where the landings were all to full stop, using various flap configurations and executing both three-point and wheel landings. The landing surface at Y58 was reported as "rough." The airplane was then flown to D42 where three landings were completed without incident. The flight instructor indicated the pilot was not getting full aft control movement in to "pin the tail to the runway." The pilot, in part, stated:

The accident landing proceeded normally with a smooth mains

touchdown and reduction of speed until the tail settled. I move[d] the

control yoke from full forward to full aft, at which time the tail of the

aircraft abruptly moved the left. Full left rudder and application of

power did not stop the movement, and we entered a ground loop to

the right. I cut power, and the aircraft came rest approximately 10 feet

off the right side of the runway.

At 1553, the recorded weather at the Redwood Falls Municipal Airport, near Redwood Falls, Minnesota, located about 19 nautical miles and 350 degrees from the accident site, was: Wind variable at 3 knots; visibility 10 statute miles; sky condition few clouds at 6,500 feet; temperature 31 degrees C; dew point 12 degrees C; altimeter 30.14 inches of mercury.

The pilot further indicated that one of the three leaf springs of the tailwheel assembly was broken and this break occurred sometime between takeoff and the conclusion of the accident landing at D42. Eighteen landings were estimated to have been conducted during that time frame. This break reportedly reduced the stiffness of the tail gear and allowed the tailwheel to twist from its vertical position and applied a strong force to the left that could not be corrected by application of full left rudder. The pilot reported that the spring accumulated 3,181 hours of total time and 4 hours since an annual inspection.

A Federal Aviation Administration inspector examined the airplane and observed the broken spring. The inspector confirmed the separation in the spring and indicated that the separation was consistent with overload.

NTSB Probable Cause

The tailwheel spring's overload failure during landing, resulting in a ground loop and runway excursion.